Product How-To: Interoperability comes to EDA

Engineers often need to move between Tanner and Mentor Graphics EDA tool sets several times in the design flow. Paul Double, founder and CEO of EDA Solutions, explains how Tanner’s External Verification Interface (EVI) maintains the integrity of the data and how companies can operate more efficiently while keeping tool costs down.

It is common for IC designers to deal with a heterogeneous or multi-tool flow, moving between tools for compelling business reasons. Even though most designs require only a fraction of the functionality and expense of a Mentor Graphics tool suite, some companies purchase full Mentor Graphics tool seats for occasional, large, or complex designs. Many foundries consider Calibre the gold standard for physical verification for full chip sign-off, so designers may obtain Calibre licenses and use Tanner Tools for layout and schematic entry. There is also the learning curve - designers in small companies need easy-to-use, affordable, PC-based tools they can learn quickly for most of their work, while still needing Mentor Graphics tools for complex applications and foundry standards.

However, the back-and-forth movement of files in a multi-tool flow is inefficient and potentially risky. As designers work around binary incompatibilities and move text files from one system to another, this flow broadens the potential for error and introduces several potential problems. One wrong move during the export/import step could result in the use of the wrong file at best, or at worst, in loss or corruption of data. Interoperability among EDA tools removes the manual step and minimizes this risk.

Time and efficiency also need to be taken into account. A layout engineer may run DRC several hundred times during a project, and having a multi-tool flow can increase DRC- or LVS-time by up to two minutes per run. Interoperability can greatly shorten a design project. And because multi-tool flow can be cumbersome and time-consuming, layout engineers may hold off on running DRC/LVS, thereby leaving problems undetected until late in the project, when it generally takes longer to address them. Interoperability improves designers’ productivity and encourages ongoing DRC throughout the project instead of leaving it until the end.

To help ease a multi-tool flow by adding interoperability among EDA tools, Tanner has developed its External Verification Interface (EVI) for Tanner Tools that works with Calibre RVE and Calibre Interactive. Users of Tanner’s S-Edit (Schematic Capture) and L-Edit (Physical Layout) can now enjoy integration with verification tools from Mentor Graphics; users of Mentor Graphics tools can now take advantage of Tanner’s lower cost EDA tools for physical layout and schematic capture. Both sets of users can design affordably and verify quickly to industry standards without the cumbersome, error-prone export/import step.

With the new EVI, engineers can continue to design with Tanner’s industry-standard, PC- based layout tools while avoiding the risk of errors from manually moving files back and forth between toolsets. Remote users also enjoy the portability of Tanner Tools when connecting to verification tools and results files on servers running Calibre RVE and Calibre Interactive. Tanner’s L-Edit and S-Edit display results (DRC, LVS and parasitics) from Calibre natively. The result is that IC designers who have invested in Mentor now get more value from tightly integrated Tanner Tools.

EVI is a plug-in that implements 100 percent of the Calibre Results Viewing Environment (RVE) interface, so Tanner users can now perform layout-to-schematic cross-probing without leaving L-Edit and S-Edit, greatly simplifying LVS verification. A tool flow for EVI Calibre RVE is shown in figure 1.

Mentor welcomes interactions between Calibre and third party tools, which is why we have the Mentor OpenDoor partner program to ensure access for other EDA vendors, and quality interfaces for our mutual customers. Quality assurance testing and certification is a big part of that program. Consequently, we feel obliged to inform readers when those expectations are not met.
Tanner EDA is currently not a participant in Mentorís OpenDoor program, and the External Verification Interface described in this article is not validated or supported by Mentor Graphics. With the growing complexity of advanced verification flows, users should be concerned about errors in the transfer of data between tools, and they should expect that interoperability interfaces are thoroughly tested by all the vendors whose tools are party to the exchange.

One of the most pernicious problems with tool interoperability is file skew--a prerequisite file, like a library or a verification result that is out of date. Once it gets into your data, file skew causes subtle errors that necessitate a tremendous amount of rework.
How does your Tanner-Calibre interface address file skew?
I share what I know about IC design flow control at
http://www.voom.net/controlling-your-ic-design-flow